// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SKY_ENGINE_CORE_EDITING_COMPOSITIONUNDERLINERANGEFILTER_H_
#define SKY_ENGINE_CORE_EDITING_COMPOSITIONUNDERLINERANGEFILTER_H_

#include "flutter/sky/engine/core/editing/CompositionUnderline.h"
#include "flutter/sky/engine/wtf/NotFound.h"
#include "flutter/sky/engine/wtf/Vector.h"

namespace blink {

// A visitor class to yield elements of a sorted (by startOffset) list of
// underlines, visiting only elements that intersect with specified *inclusive*
// range [indexLo, indexHi].
class CompositionUnderlineRangeFilter {
  WTF_MAKE_NONCOPYABLE(CompositionUnderlineRangeFilter);

 public:
  class ConstIterator {
   public:
    ConstIterator() : m_filter(nullptr), m_index(0) {}
    const CompositionUnderline& operator*() {
      ASSERT(m_index != kNotFound);
      return m_filter->m_underlines[m_index];
    }
    ConstIterator& operator++() {
      if (m_index != kNotFound)
        m_index = m_filter->seekValidIndex(m_index + 1);
      return *this;
    }
    const CompositionUnderline* operator->() {
      ASSERT(m_index != kNotFound);
      return &m_filter->m_underlines[m_index];
    }
    bool operator==(const ConstIterator& other) {
      return other.m_index == m_index && other.m_filter == m_filter;
    }
    bool operator!=(const ConstIterator& other) { return !operator==(other); }

   private:
    friend class CompositionUnderlineRangeFilter;

    ConstIterator(CompositionUnderlineRangeFilter* filter, size_t index)
        : m_filter(filter), m_index(index) {}
    CompositionUnderlineRangeFilter* m_filter;
    size_t m_index;
  };

  CompositionUnderlineRangeFilter(
      const Vector<CompositionUnderline>& underlines,
      size_t indexLo,
      size_t indexHi);

  ConstIterator begin() { return ConstIterator(this, seekValidIndex(0)); }
  const ConstIterator& end() { return m_theEnd; }

 private:
  friend class ConstIterator;

  // Returns |index| if |m_underlines[index]| intersects with range
  // [m_indexLo, m_indexHi]. Otherwise returns the index of the next
  // intersecting interval, or END if there are none left.
  size_t seekValidIndex(size_t index);

  // Assume that elements of |m_underlines| are sorted by |.startOffset|.
  const Vector<CompositionUnderline>& m_underlines;
  // The "query range" is the inclusive range [m_indexLo, m_indexHi].
  const size_t m_indexLo;
  const size_t m_indexHi;
  const ConstIterator m_theEnd;
};

}  // namespace blink

#endif  // SKY_ENGINE_CORE_EDITING_COMPOSITIONUNDERLINERANGEFILTER_H_
